Soft bag charging lithium battery: Analysis of the influencing factors of heat sealing process

Soft bag charging lithium battery: Analysis of the influencing factors of heat sealing process

The design of aluminum plastic film is high, and the manufacturing technology is required. At present, 90% of the domestic market is important from Japan’s DNP / Showa Electric, South Korea, monopolized, domestic companies such as Xinyi Technology, Buddha’s Plastics, etc. Accelerate the development and production of aluminum plastic films, but there is still a gap compared with Japanese companies.

At present, the packages of lithium-ion batteries on the market are important to square packages, cylindrical packages, and aluminum film packages.. Square packages and cylindrical packages are important in metal shells, including aluminum shells and steel shells.

Aluminum-plastic film package Important applied to soft bag lithium ion battery packaging. Important applied to the 3C field with an aluminum-plastic film packaged soft bag, in recent years, it has gradually penetrated into the new energy automotive industry, providing safe and stable power output for each model of automobile..

With the continuous improvement of dynamic lithium-ion battery production technology and the development of new batteries is constantly accelerating, the national performance requirements of the dynamic lithium-ion battery are more strict, the government subsidy standard is continuously improved, the amount of subsidies is gradually reduced until no subsidy formation Promote technology development. The advantage of the fittest is the market’s law, the energy density, safety, and cost of the lithium-ion battery must be strictly controlled..

In three lithium-ion batteries, the soft boiled lithium battery has the advantage of small mass, small internal resistance, high safety, high energy density, and is important in the field of power lithium battery.. First, the aluminum-plastic film introduction to the package material used by the lithium ion battery is an aluminum-plastic composite film, referred to as aluminum plastic film.

The design of aluminum plastic film is high, and the manufacturing technology is required. At present, 90% of the domestic market is important from Japan’s DNP / Showa Electric, South Korea, monopolized, domestic companies such as Xinyi Technology, Buddha’s Plastics, etc. Accelerate the development and production of aluminum plastic films, but there is still a gap compared with Japanese companies.

The thickness of the aluminum plastic film has different specifications, and its structure is important to comply with three materials, from the inside to the outside of the CPP layer, Al layer, nylon layer, as shown in Figure 1. Figure 1. Basic composition of the aluminum plastic film is packaged before the bare core is packaged, and the aluminum film is diced, and the aluminum plastic film is rushed to the required specifications, the battery is packaged.

. The innermost material of the punching pit is a cast polypropylene film (CPP) having a certain melting point, and both surface CPP layer materials are melted and bonded together at a certain temperature and pressure, as shown in Figure 2..

The CPP layer material and the metal Ni, Al, and the ease glue have good thermal sealing bonding, which itself has good electrolyte and anti-HF properties, and the CPP layer also has better insulation and physical protection performance, which can effectively prevent Short-circuit between the electrode and the lithium ion battery soft bag material caused by aluminum film corrosion. In the middle of the Al layer material is an important purpose of preventing water from moisture in the air, moisture penetrating into the electrical core and the electrolyte reaction to form HF and form a large amount of gas, resulting in a lithium ion battery, is one of the important hidden dangers of lithium ion batteries..

The Al layer has a certain intensity to prevent external force from damage to the battery.. The outermost nylon layer is important to prevent the infiltration of oxygen in the air, maintain the internal environment of the battery.

The outermost layer is also due to its well-duplex performance, in the early aluminum-plastic film, in the early aluminum film, PET is used, but due to the PET itself, it causes bending and moldability. The method of manufacturing the aluminum plastic film is important for both heat law and dry method. The thermal process is the use of MPP bonding between aluminum layer and CPP layers, hot pressing at a certain temperature.

. The MPP in MPP is destroyed, aging, and short-circuit performance will drop sharply..

At the same time, since the molecular structure is destroyed, the toughness is lowered, and it is easy to rupture during the molding process.. The dry process is directly composite to the binding agent in the middle of the PP and aluminum layer, and the insulating binder is used, and there is no need for high temperature treatment.

. Moreover, the binder itself is better than the PP layer, and does not affect the molding..

Figure 2. A hot seal of an aluminum plastic film 2, the heat sealing influencing factors, first understand that the purpose of the aluminum plastic film is completely separated by the electrical cell and the outside environment, that is, everything possible to affect the external moisture, air Infiltration, poor packaging of electrolyte leaks should not appear. The soft bag core package is important to the top side seal and the final sector.

The top-seating process is important is an aluminum mold, a very henite and a copper nickel direct package, with a large damage possibility.. The side seal is the package between the aluminum mold CPP layer, there is not much problem, it is important to prevent pleats and bubbles.

. The final seal is a vacuum package. Since the lithium ion battery pre-charged, the electrolyte is also easily sticky to the aluminum-plastic film PP layer, resulting in poor packaging.

During the production process, the technician often uses six aspects of the method of recurrence of the method of failure.. First, we need to exclude the subsequent influencing factors, and the secondary influencing factors have a person, environment and test method.

. Personnel’s operating level and work-related experience have a certain impact on the encapsulation effect, where we set a person’s operational level is certain and there is no problem..

The test method is certain, and the inspection of the encapsulation effect is obvious, do not perform an abnormal analysis. Before the package is carried out, it is necessary to clean and confirm the workshop environment, including desktop foreign matter, impurities, and humidity, etc., everything can be used, and it is not discussed here.

. The following will analyze important factors affecting the heat sealing effect, namely materials, equipment and processes. 1.

Material incoming inspection is an important means of preventing abnormal inflows, and is also an important means of reducing unqualified product and reducing production costs.. In terms of the incoming material in the package process, it is two aspects: one is the aluminum plastic film itself, and the second is the bare cell.

. The aluminum plastic film itself is abnormal, including the abnormalities of the aluminum film itself..

The aluminum plastic film itself should observe whether its color is normal, whether there is air bubble, stain, scratches, etc.. Other properties of aluminum plastic film itself will supply corresponding test data, such as aluminum foil and PP layer peel strength, processing performance, anti-permeability, etc.

. Lithium-ion battery companies will also conduct corresponding inspections to confirm the investment. Aluminum plastic film pits is for the good, beautiful and puddle introduction of CPP damage, unusual pits, etc.

. The key to the quality of the pit is the design of the punch abrasive, and the punch grinding is important with a die, a punch, a pressure plate, and other auxiliary devices. The length, width, and depth of the mold are required according to the shape of the battery.

. According to the gap of the uneven die according to the punch depth, the surface roughness of the surface of the aluminum plastic film processing characteristics is designed according to the aluminum plastic film..

The problem of important existence of bare choeic cores is that there is pollution on the surface of the ears, which may cause poor packaging.. 2.

The design of the equipment and equipment mold, structural design is undoubtedly important to the package effect.. In the top segmentation process, there is an uneven contact surface between the aluminum-plastic film and the polar glue, which must be bonded to the PP layer of the case where the case of the PP layer and the outer surface of the absorbent film PP layer and the outer surface of the ultra-ears.

Further, it is necessary to ensure that the bonding of the PP level of the non-extreme oozie aluminum plastic film is good.. The selection of the equipment package mold design and the selection of the head can be compared to the hard seal, which can be used to add silica gel on the hard seal.

The deformation of silica gel is used to compensate for the lack of the top seal, or the hard-sealed mold can be used. Digging a groove to make a package. Do not consider so much when using soft seals, but pay attention to soft sealing packages, verify the sealing of the package, and the aging problem of high temperature glue.

The package thickness is too large or too small, which is not conducive to the encapsulation of aluminum plastic film. The thickness is too large, and the aluminum-plastic film is not packaged. It may be unstable due to small pressure or sensor abnormality.

. The package thickness is too small means that it is sealed, which may cause the PP layer to overcome, expose aluminum layer..

Adding a corresponding limit device on the device to achieve the best package effect. In addition, the temperature sensor will also cause the set process temperature to be not reached, causing an overlay or arrelect, resulting in poor packaging..

3. Process packing process is the most critical influence, key factors in packaging process have temperature, pressure and time. The optimum state of the package is that the PP film reaches the melting point, bonded together, the package appearance is good without bubble-free wrinkles, high package strength, good sealing, through insulation test.

The package strength is tested with a tensile test machine, and the schematic shown in Figure 3 is shown.. In addition, lateral stretching and longitudinal stretching can be selected in the sample stretching mode, the tensile testing machine has a horizontal tensile testing machine and a vertical tensile testing machine.

Generally, the vertical test machine generally said electronics. Universal testing machine, sensor is on the mobile, so vertical can do peeling, stretching, compression, sharpness these tests. In terms of stability, a special horizontal testing machine to be a bitter, which is a bit better, and both should choose the measurement of the appropriate sensor.

. The appearance is tested by visual inspection, and the sealing is tested by vacuum..

The insulation test is an instant high pressure to the ears and aluminum plastic film to test whether the package is good, detect a non-good product in advance, preventing the flow of defective products. Figure 3. Package intensity drawing In the use of a aluminum-plastic film, it is necessary to perform temperature, pressure and time three factors to confirm the best package process.

. The PP melting temperature of the aluminum plastic film is generally at 180 ¡ã C to 190 ¡ã C, and several temperature points can be selected for the same pressure and the heat sealing experiment of the heat sealing time, and the optimum package temperature is determined by heat sealing strength and effect..

Corresponding, it is also possible to determine the impact of heat sealing pressure and time on intensity and packaging effect.. After the correlation analysis, which factor can be confirmed as an important factor.

In general, the encapsulation strength increases with the encapsulation temperature, and when the temperature reaches a certain height, it may cause a high seal, PP melt glue overflow the heat sealing area, and then form cracks to reduce the heat sealing strength.. The hot sealing is preferably related to the temperature, the temperature is low, and the thermal seal time has little effect on the intensity, because the PP layer does not reach the melting point at low temperatures, the heat sealing layer is not fused together.

. When the temperature is high enough, the heat sealing time and the heat sealing strength are positively correlated. Package pressure can affect the thickness of the package, but it is less important factor associated with temperature and time.

. Pay attention to the flatness, parallelism of the head in the daily package equipment, and the temperature sensor is normal. When the temperature is abnormal, the corresponding problem should be solved.

. The battery pack is a key process that affects the ultimate performance of the battery. The encapsulation factors of aluminum plastic film have important equipment and mold selection.

The determination of packaging processes, packaging temperature and package time in the package process have important positions.. Secondary influencing factors have the quality of the feed, the capacity of the operator, and the workshop environment, etc.

. Only in each aspect is well coordinated, it can do a good as the electrical core package. When the electrolyte corrosion is prevented, the internal and external environment is separated from the outside to the external environment, preventing the penetration of water vapor, ensuring the cycle life of the lithium ion battery and safety.

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